Waiting for commercially viable catalysts, apparently.

Fuel cells are the dream power source for vehicles: they can use hydrogen and oxygen as fuel and oxidizer, respectively, and produce only electricity and water (plus a little heat). Compared to battery-powered electric vehicles, hydrogen-powered fuel cell vehicles offer higher energy density, which leads to greater range and lower weight. Sure, they have their downsides—such as requiring a complete hydrogen infrastructure à la oil pipelines and fueling stations—but batteries vs. fuel cells is a debate for another day (and story).

The first hydrogen fuel cell vehicle (General Motors/Chevy Electrovan) was created in 1966. Researchers have been developing proton exchange membrane (PEM) fuel cells for past 15 years. So why don’t we see any in cars on the road? In a word: catalysts. Despite intense development, catalysts used in PEM fuel cells haven’t reached the levels of performance, lifetime, or cost to be commercially viable. In a recent issue of Nature, Mark Debe, senior scientist in the Fuel Cell Components Program at 3M, summed up the recent progress and prospects for fuel cell catalysts, including potential manufacturing issues.

The basics

First off, what is a catalyst? How does a fuel cell even work? What is the air-speed velocity of an unladen swallow? (African or European?) One question at a time, please.

In brief, a fuel cell directly converts the chemical energy locked in a fuel (like hydrogen) into electricity though a reaction with an oxidizer (typically, oxygen). All fuel cells consist of an anode, cathode, and electrolyte, which classifies the type of fuel cell (for example, in a PEM fuel cell, the PEM is the electrolyte) and allows the charges to move between the anode and cathode.

In the case of hydrogen and oxygen in a PEM fuel cell, hydrogen is split on the anode side into protons and electrons. The protons travel through the membrane electrolyte while the electrons move through an external circuit—generating an electrical current—to the cathode, where oxygen molecules react with the arriving protons and electrons to create water.

Each individual fuel cell generates only a small amount of electricity (less than a volt), so the overall “fuel cell” is actually a stack of a couple hundred cells. Each cell, or membrane electrode assembly, is comprised of the two electrodes (anode and cathode) sandwiching the PEM, surrounded by porous gas diffusion layers that bring the fuel and air in and water out.

The overall reaction occurring in a fuel cell is the same as when you burn hydrogen: hydrogen plus oxygen produces water and energy. In both cases, the energy of the system must reach a certain activation level before the reaction will proceed. In the case of combustion, this is done with an ignition source such as a high-temperature spark. PEM fuel cells, on the other hand, operate at much lower temperatures. This is where the catalyst comes in: it effectively lowers the activation energy by increasing the reaction rate without being consumed in the process. (By contrast, solid oxide fuel cells operate at much higher temperatures and therefore don’t need a catalyst).

The most effective catalysts in hydrogen fuel cells use platinum for both the anode and cathode. Here is the problem (one of the problems, at least): platinum is expensive. Right now, the cost is over $1400 per troy ounce, just under that of gold. Most catalyst research focuses on how to use less platinum (or none at all) while simultaneously increasing performance and durability.

With all this in mind, let’s take a look at where we are now.

Current performance

You may not realize it, but we actually do have some cars running on hydrogen on the road. The US Department of Energy (DOE) teamed up with a couple major car manufacturers (Ford, Hyundai, Kia, Daimler, and GM) to test a total of almost 200 vehicles. According to DOE reports, these test fleets used at least 0.4 milligrams of platinum per square centimeter on the cathode alone. The goal for 2017 is to use 0.125 milligrams per square centimeter of platinum group metals (which includes ruthenium, rhodium, palladium, osmium, iridium, and platinum) total between the anode and cathode. In a fuel-cell assembly rated at eight kilowatts per gram of platinum, this works out to eight grams total per vehicle—close to what is used in current internal combustion engines (in the catalytic converter).

According to a DOE technical plan, as of 2011 we’ve reached a power density of about 5.3 kilowatts per gram of PGM, and 0.15 milligrams of PGM per square centimeter—nearly there. However, the stability of the catalyst isn’t yet where we need it, limiting the lifespan to below the 5,000 hour target (corresponding to about 150,000 miles).

There are two conventional platinum-based catalyst approaches. The first uses “Pt blacks,” which are extremely small platinum particles that absorb light very well and appear black, with high surface-to-volume ratios—ideal for a catalyst, where the reaction activity occurs on the surface. The second involves platinum nanoparticles spread onto larger carbon black particles. However, both of these approaches would require far too much (expensive) platinum to reach the performance and durability goals necessary for use in commercially viable fuel cells.

Faced with the difficult task of improving catalyst performance but at the same time using an equal or less amount of platinum, researchers decided to simply design new catalyst nanoparticles.

New catalyst designs

Debe classified the new designs for platinum-based catalysts into four categories. The first, extended surface area catalysts, is fairly self-explanatory. By increasing the surface area, such as by applying thin films on particles or using a porous film, these catalysts can increase reaction activity while using less platinum in the process.

The most promising approach in this category appears to be nanostructured thin-film (NSTF) catalysts. In these, a thin film of a platinum alloy coats a tiny, thin layer of crystalline, organic whiskers. Each whisker is less than a micrometer tall and over 2,000 times thinner than a human hair. Since NSTF catalysts are so thin, the volume is low, resulting in a high surface-area-to-volume ratio. In addition, the organic whiskers are not conductive, preventing any corrosive electrical currents.

The second category involves platinum or platinum-alloy nanoparticles on low-aspect-ratio carbon black or oxide support particles. This is similar to the conventional approach using platinum nanoparticles, except now the size and shape of the nanoparticles are controlled to increase reaction activity and reduce the amount of platinum. The sizes are on the order of nanometers, and the shapes include octahedra, cubes, and more exotic shapes like truncated octahedrons.

Another promising approach in this category uses core-shell nanoparticles (think of a hollow ball). In these, the amount of platinum is reduced significantly since it is removed from the core, and the reaction activity can be increased by filling the core with a material that optimizes properties of the surface platinum layer. Core materials include palladium and palladium alloys with cobalt, iron, iridium, and gold, as well as alloys of other metals like gold and nickel. There are some issues to overcome with these catalysts, though. The performance in actual fuel cells wasn’t as high as in laboratory tests, and researchers need to develop a scalable manufacturing process capable of generating the particles without leaving a pinhole in the platinum layer (to protect the core from leaching).

Other categories of new platinum-based catalysts include nanoparticles on high-aspect-ratio supports (like carbon fiber or nanotubes) and unsupported nanoparticles (such as lone platinum nanotubes or nanoparticles). No specific catalyst designs in either of these have demonstrated particularly high performance yet, however.

What about avoiding platinum—and its high costs—altogether? Researchers have investigated catalysts using palladium and its alloys, but the performance can barely reach that of conventional platinum-based catalysts. Plus, the price isn’t that much cheaper.

Recently, according to Debe, catalysts avoiding precious metals altogether—using metals such as cobalt and iron—have demonstrated huge performance improvements. For example, an iron-based cathode catalyst reached about a tenth of the current density of platinum-based cathodes. However, the lifetime of such catalysts appears to be shorter at the voltage potentials necessary for use in vehicle fuel cells, so this area still needs some work.

Prospects

Given all of these different approaches under development, which are the most promising? Several of the concepts mentioned above—in particular, the NSTF and shape/size-controlled nanoparticle catalysts—appear to perform at levels necessary to meet DOE targets. Even commercially available platinum-alloy/carbon catalysts come close, although the durability isn’t yet where it needs to be.

Of course, even the most promising catalyst technology still has to be manufactured. Up until now, the quantity of catalysts required for the small number of test vehicles (less than 200 for the DOE studies) didn’t pose much of a challenge. DOE cost targets are based on half a million fuel-cell vehicles produced per year, and the numbers start to get much bigger if the technology is to spread into the larger world market.

To demonstrate the scales involved in manufacturing fuel-cell catalysts for a large number of vehicles, Debe ran some numbers. Producing fifteen million vehicles (ten percent of the global market in 2030) would require 4.5 billion individual fuel cells if each stack contained 300 cells (each about 300 square centimeters in area). Given a production line operating at full capacity, this requires around 11,700 individual cells per minute (worldwide). Cars are produced around one per minute in each production line, so to match this, 20 fuel-cell lines would have to each produce 10 fuel cells a second.

What about the catalyst, which we’ve spent so much time talking about? At the target area density for platinum of 0.1 milligrams per square centimeter, the electrodes will be less than two micrometers thick—meaning precision coating methods. To produce the number of fuel cells needed, the production lines will have to run at 20 meters per minute. This would require one and a half kilograms of platinum per hour, or nearly $1.7 million worth of platinum in a day. Every day, per manufacturing line. This may seem high, but it is similar to the cost of platinum group metals already used in cars—that is what the target density is based on.

According to Debe, these manufacturing requirements will lead to a catalyst-coating approach similar to that already used to produce most multi-layer optical-film-coated glasses: all-dry vacuum coating. In that sector, manufacturers are already making 250 million square meters of glass per year—far more than the 135 million square meters of catalyst than would be needed.

Debe believes that, based on current progress, catalyst performance will peak in a few years well above the DOE goals for 2017. In fact, he argues that improving performance shouldn’t be the primary goal of researchers at this point—catalysts are already where they need to be. Instead, research should focus on creating catalysts that not only hit the durability and power targets, but can be manufactured at high volumes.

According to the article, there is cause for optimism. Recent developments in new kinds of catalysts offer higher performance without reducing the lifetime or increasing the cost. However, it will still be a few years before any of the newer concepts can be incorporated into realistic fuel cells, with the issue of high-volume manufacturing looming in the approaching horizon.

Promoted Comments

Even with an affordable catalyst it seems unlikely that anyone is going to bother building a hydrogen distribution network when battery tech can be at the very least "good enough". Possibly there will be applications in specialist areas (like buses, industrial vehicles etc), though perhaps the most interesting applications will be static, replacing gas generators such as those used as hospital backups and near urban areas (Bloom Energy, which has features here a few times, is in exactly this space).

I think another issue, which no one seems to have considered, is the development synergies that exist in battery cars but don't in fuel cells. Car makers have talked up fuel cells for decades but were never really that excited about making them, it wasn't much more than greenwash.

I believe the reason electric cars have suddenly made it big is because of portable electronics - all the investment went in to battery technology to make ipods and laptops better, and the car industry was able to take advantage of that. Battery cars suddenly became viable even though car makers had not invested much nor shown much enthusiasm until recently.

Unless you some how magically find unbound hydrogen in nature, it's a horrible idea. It takes too much energy or carbon emissions to produce it.

There are promising research on algae/artificial photosynthesis. Producing hydrogen is not a problem. Transporting it is.

I disagree about carbon emissions. Running car on conventional fuel is also carbon emitting. There are cleaner ways to make hydrogen but there isn't cleaner ways to use fossil fuels. In my book hydrogen wins. I haven't mentioned air pollution from ICE. The world is so much better without car exhaust fumes.

Unless you some how magically find unbound hydrogen in nature, it's a horrible idea. It takes too much energy or carbon emissions to produce it.

There are promising research on algae/artificial photosynthesis. Producing hydrogen is not a problem. Transporting it is.

I disagree about carbon emissions. Running car on conventional fuel is also carbon emitting. There are cleaner ways to make hydrogen but there isn't cleaner ways to use fossil fuels. In my book hydrogen wins. I haven't mentioned air pollution from ICE. The world is so much better without car exhaust fumes.

Well carbon emissions from liberating hydrogen from organic compounds is what I meant, particularly methane.

I still think in the long run, hydrogen will lose compared with batteries - what will most likely end up happening is that we'll see in around 2025 is the plug-in hydrogen vehicle. The battery will be enough for ~50 miles of daily driving, and the hydrogen fuel cell stack will take over from there with an additional 350 miles of range beyond that. This solves many of the problems associated with hydrogen fuel cells - longevity, slow changes in output energy, large scale infrastructure, etc. I don't think my range extender has more than 5 hours of use in 2,200 miles of driving my Volt so far, so 5,000 hours would last me 2.2 million miles (unlikely it'll last that long, but it might allow for alternate materials with less durability to be substituted). The fuel cell stack cant change output energy rapidly, so all fuel cell vehicles now have a battery in them to buffer output. And since most people will travel on electricity, we don't need to duplicate our gasoline infrastructure 1:1 with hydrogen facilities, we can replace our gasoline infrastructure with about 30-40% of equivalent hydrogen infrastructure.

An aqueous fuel cell, that needs to be supplied only with fresh or salt water, has been invented by Dr. Nguyen Chanh Khe, Scientific Director of a Research and Development Center in Vietnam, and his associates. Early prototypes generated 50W of power. Latest examples produce 2,000W and 2,400W. Power is expected to eventually reach up to 600kW. Dr. Khe says this is an opportunity for Vietnam, and later the world, to obtain cheap electricity.

BlackLight Power claims six independent scientists have completed validation studies confirming that their CIHT fuel cell represents a breakthrough technology. An 89 page paper has been posted on the BLP website detailing the cell chemistry and operation.Fueled by water vapor, the CIHT cell currently produces 10 watts of electric power. With further development, it is claimed it will provide 1,500 watts for low-cost home power generation before the end of next year. BLP anticipates it will later power electric cars, with no fuel other than water required. They earlier stated it will eventually allow a car, the size and weight of a Prius, to travel more than 5,000 miles on a gallon of ordinary water. Capital cost is anticipated to be well below that of any existing power generation system. The claims have been greeted with great skepticism by much of the scientific community.

See Moving Beyond Oil on the Aesop Institute website to learn more about both.

Unless you some how magically find unbound hydrogen in nature, it's a horrible idea. It takes too much energy or carbon emissions to produce it.

There are promising research on algae/artificial photosynthesis. Producing hydrogen is not a problem. Transporting it is.

I disagree about carbon emissions. Running car on conventional fuel is also carbon emitting. There are cleaner ways to make hydrogen but there isn't cleaner ways to use fossil fuels. In my book hydrogen wins. I haven't mentioned air pollution from ICE. The world is so much better without car exhaust fumes.

Carbon emission isn't the only issue with conventional internal combustion engine. It emits whole lot of other random crud that is probably slowly killing us all at ground level.

Actually, there is a corporate political concern here as well. In 2003 you could find a few various companies putting out actual fuel cells as alternative power for homes. Most then were between $2k for a single family residence, up to about $8k for a small compound. You could search websites like hgtv and easily find them. (HGTV had done some stories on these fuel cells.) However, there has been a consorted effort by utility companies to buy fuel cell companies, which the devices are then converted and repackaged as expensive forms of "backup power". Those fuel cells used either natural gas, or propane to convert into power. Of course both easily could be used to power fuel cells in vehicles of all kinds. Unfortunately that cheaper technology is locked up because it is a huge threat to power companies. Imagine if you had a fuel cell in your home that only cost a couple of grand, or less after they were more widely available, powering your home for pennies, Vs. hundreds of dollars each month. You also get some really desirable side effects, like not worrying about brown outs, black outs, terrorist attacks on the utilities, or mother nature. You also help solve water shortages with the water byproduct and end things like coal, or nuclear pollution. Sad we don't have this already for our cars, let alone for our homes and small businesses.

Even with an affordable catalyst it seems unlikely that anyone is going to bother building a hydrogen distribution network when battery tech can be at the very least "good enough". Possibly there will be applications in specialist areas (like buses, industrial vehicles etc), though perhaps the most interesting applications will be static, replacing gas generators such as those used as hospital backups and near urban areas (Bloom Energy, which has features here a few times, is in exactly this space).

I think another issue, which no one seems to have considered, is the development synergies that exist in battery cars but don't in fuel cells. Car makers have talked up fuel cells for decades but were never really that excited about making them, it wasn't much more than greenwash.

I believe the reason electric cars have suddenly made it big is because of portable electronics - all the investment went in to battery technology to make ipods and laptops better, and the car industry was able to take advantage of that. Battery cars suddenly became viable even though car makers had not invested much nor shown much enthusiasm until recently.

Whoa. The catalyst isn't the major problem: it's the hydrogen fuel. Hydrogen simply doesn't exist in (separated) liquid form anywhere on earth. Yes, it's abundant, but in the form of different organic molecules and (most notably) water. The current methods for creating viable liquid hydrogen fuel require so much carbon output that it undermines the entire point of using fuel cells. It's highly misleading to suggest that Platinum target will be met on or before 2017 when the big problem is so vast, that is hardly being addressed. I really don't know if there is any viable way to create hydrogen fuel without a massive cost both in terms of $$$ and the environment. Some people have suggested electrolysis using power from nuclear power generation, but that wouldn't exactly make environmentalists very happy either.

They earlier stated it will eventually allow a car, the size and weight of a Prius, to travel more than 5,000 miles on a gallon of ordinary water.

Amazing! ...given the fact that water is a relatively low energy molecule compared with H2 and much larger hydrocarbons the implied energy densities would travel well outside of realty and least for a chemical process and I doubt a nuclear process is at play... but it should be trivial to find funding to make this real given what you say (of course I would feel bad for those that fall blindly for this scam)...

...of course I call bullshit (complete bullshit) but heck I would love to be proven wrong.

An aqueous fuel cell, that needs to be supplied only with fresh or salt water, has been invented by Dr. Nguyen Chanh Khe, Scientific Director of a Research and Development Center in Vietnam, and his associates. Early prototypes generated 50W of power. Latest examples produce 2,000W and 2,400W. Power is expected to eventually reach up to 600kW. Dr. Khe says this is an opportunity for Vietnam, and later the world, to obtain cheap electricity.

Not the "car running on water" crap again. Could you please not post scams that would violate the first law of thermodynamics to work?

All such scams do not use "just water". They use electricity to run. They perform electrolysis on the water with it. Then they use the resulting hydrogen gas to either generate electricity in a fuel cell, or burn it directly in the car engine. Then they claim that the output energy obtained is higher than the electric energy used to power the system.

Of course their inventions "work". But they are useless. They do not generate energy from water. They transform electric energy into other forms of energy, with very high losses.

The Water Fueled Fuel Cell in Vietnam may be in production shortly. The inventor holds 37 U.S. Patents. Most obtained as a Senior Engineer with Hewlett Packard and Kodak.

Think about it.

How is this thing suppose to work, exactly? Does it require a huge gasoline driven electrical generator that sends many dozens of kilowatts of electricity into the 'water fueled cell' to generate the hydrogen necessary to run a motor?

The guy could have four hundred patents to his name working as a nuclear scientist/rocket engineer/brain surgeon and it's still not going to change the laws of nature.

It's not going to change the fact that water and hydrogen is NOT a power source. And it's not going to change the fact that you are only going to get back about 50-60% the energy you put into generating the hydrogen.

BlackLight Power has been in business about 20 years and raised $75 million in venture capital. Their CIHT claims are based on fractional Hydrogen, which they have trademarked as hydrinos.

Our own work with fractional Hydrogen suggests they are correct that a barrel of water can replace 200 barrels of oil. See the Chava Energy website.

Scaling from the present 10 watts is the real challenge with their system. This is new science. In our opinion, their theory contains errors. However, it is conceivable they will succeed at getting the power level to 100 watts which they claim is the goal for this year, and 1,500 watts next year.

The water fueled fuel cell in Vietnam has already exceeded 2kW. And that work is well financed by a Japanese partner firm. 200 samples are being fabricated for Japan.

April 2007: Antonio Di Castro showed that the states below the ground state, as described in Mills' theory, are incompatible with the Schrödinger, Klein-Gordon and Dirac equations

Quote:

Mills claims he has unified Maxwell's Equations, Newton's Laws, and Einstein's General and Special Relativity on the basis that they must hold on all scales from the subatomic to the cosmic. Mills has put forward his thesis in his book, originally called The Grand Unified Theory of Classical Quantum Mechanics (GUT-CQM), and later given the new title The Grand Unified Theory of Classical Physics (GUT-CP).

BlackLight Power has been in business about 20 years and raised $75 million in venture capital. Their CIHT claims are based on fractional Hydrogen, which they have trademarked as hydrinos.

The water fueled fuel cell in Vietnam has already exceeded 2kW. And that work is well financed by a Japanese partner firm. 200 samples are being fabricated for Japan.

Scammers (and crackpots) often travel in packs, and offer mutual support. I remember similar when the Nuclear powered car idea was floated a while back, you could follow the founders links to other supporting scammer/patners, and then Google them and discover the charges they were facing from the SEC for complete sham they were selling to investors.

Then you have long running scams like EEStor, that manage to keep fleecing investors with enough techno-babble.

The technology to have a computer screen inside a car that allows internet browsing is available today. All that we need to do is finish up the development of cars that use power generated from masturbation and the whole energy problem is solved. Then again, do we need more jerks on the road?

Given all of these different approaches under development, which are the most promising?

How about avoiding the catalyst regulations all together and use a milk carton to catch the water deposit with instead? We promise we would emptied the milk carton at the end of the day and we won't complain about the inconvenience? While these regulations of air pollution making our lives so miserable.

Our lives were the same pre-catalyst era. Were we?

Quote:

or nearly $1.7 million worth of platinum in a day.

Not when this under the full production lines. The cost of platinum will shoot up much higher than its current market value today, and that's for sure. Demand and supply?

And when centuries later. We'll be facing the shortage of platinum. What are we going to do then? We use gold plated instead? No more glass productions?

Nice article, though it only focuses on the catalyst part of the whole idea. Fuell cells have been "around the corner" for more than a decade now, and research goes back even further. I know, some are already in use. There are a couple of test fleets, not only in the U.S. A couple of cities employ fuel cell public transportation (where the distribution network is no problem). You can get fuel cell backup generators. And there is a number of fuel cell based submarines (Israel just retrofitted a few german models for use with nukes, was just in the press recently). So the tech is definitely mature, even military grade.

What keeps it from cars are the other problems, not just platinum availability (btw: battery cars have a way bigger problem if lithium cars get widespread, there's not enough lithium either).The problems are storage, handling and production. What I missed with the catalyst theme is the "other" catalyst models. There have been some test in using a two stage catalytic process, where first an organic compound (Methanol, Ethanol, etc) was split and the resulting hydrogen used for fuel cells (basically a cold combustion). This would make handling and production way easier. The other question I don't see about the catalyst, what about degradation? A common problem with fuel cells is their use of air O2, which introduces all the other bad stuff in the air to the catalyst and degrades it.There are also many ideas out there for hydrogen production. Also on the catalytic side, by solar radiation, from organic compounds (i.e. from methane or natural gas, which means we could reuse the existing natural gas distribution network).Then there's storage. So much has been going on there. Most simple method is high pressure, but there were some ideas of introducing a matrix-storage (some kind of polymer, I think). Where do we stand there?

Hydrogen cars are a pipe dream. Electric cars are much more efficient in converting electricity (which you need to produce the hydrogen) to useful energy. As for hydrogen-producing algae, they still need (sun)light to work, and setting up solar power plants in the same area instead would almost always be more efficient.

The main problem of electric cars at the moment is the low energy density of current batteries, which is a much less fundamental problem than that faced by hydrogen cars.

The main problem of electric cars at the moment is the low energy density of current batteries, which is a much less fundamental problem than that faced by hydrogen cars.

There are more problems then that.

Beyond the fact that they require very large and very heavy batteries they wear out rapidly. Meaning if you get a car that claims a 60 mile range and you drive it 50 miles every day in 2 years you will probably have a 40 mile car. 2 years after that you will have a 20 mile car. Also manufacturing batteries on a large enough scale to meet world-wide demand has massive ecological consequences.

Hydrogen makes sense only when you have a massive source of cheap electricity. That way you don't care that you have 70%+ energy loss just trying to fuel a car (taking into account transmission loses, voltage conversions, and water-hydrogen conversion, etc)

This can only make sense if you were to turn to nuclear energy, which currently government regulation ineptitude and politics have rendered almost useless. There are ways to reclaim nuclear waste from current generation power plants and re-use it over and over and over again until it's pretty much inert, but nobody is allowed to do that themselves and nobody is allowed to sell the waste to other people that would do it.

Beyond the fact that they require very large and very heavy batteries they wear out rapidly. Meaning if you get a car that claims a 60 mile range and you drive it 50 miles every day in 2 years you will probably have a 40 mile car. 2 years after that you will have a 20 mile car.

Like with energy density, there's nothing fundamental about battery endurance. Battery technology is already moving forward in that area. Worn-out batteries can also be recycled into new ones.

drag wrote:

Also manufacturing batteries on a large enough scale to meet world-wide demand has massive ecological consequences.

And manufacturing fuel cells hasn't? The article already detailed the problems of mass-producing fuel cells. See also the above point about recycling.

drag wrote:

Hydrogen makes sense only when you have a massive source of cheap electricity.

Whereas electric makes sense if your energy supply is limited, which is the case.

frozentech wrote:

The problem with battery powered cars is A: You still need to make the electricity - which everyone forgets, and since no one wants Nuclear plants, that means more Coal, oil, Natural gas plants.

The difference to hydrogen cars being that you also need to make electricity to power hydrogen cars, except you need a lot more of it.

frozentech wrote:

And B: When my battery in my car is flat, I can't just plug it in and five minutes later (or less) tool off.

So for the 5-10% of driving where charging a car overnight isn't enough, you either use a hydrogen/gas/biofuel/whatever range extender, or drive to a "gas" station and swap your battery for a freshly charged one. Big deal.

Kyle Niemeyer / Kyle is a science writer for Ars Technica. He is a postdoctoral scholar at Oregon State University and has a Ph.D. in mechanical engineering from Case Western Reserve University. Kyle's research focuses on combustion modeling.